1. Field of the Invention
The invention relates to control valves usable in water softeners and other potable water conditioning units and, more particularly, relates to a control valve having a linearly reciprocating piston that is driven by a motor without imparting any significant side load to the support structure for the piston""s drive rod or the associated seals. The invention additionally relates to a method and apparatus for operating a water conditioning unit control valve so as to enhance the valve""s versatility and reliability.
2. Discussion of the Related Art
A variety of water conditioning units are available for softening, filtering, and/or otherwise treating potable water for residential and commercial applications. The most common water conditioning units are filtration systems that remove impurities from water, and water softeners that exchange undesirable ions such as calcium with more desirable ions such as sodium. Many of these water conditioning units employ a control valve for controlling the flow of water through the water conditioning unit. Some of those control valves have a movable piston that is actuated by an electric motor to connect various ports of the control valve to one another.
For example, control valves are widely used to control the regeneration cycles of water softeners. Water softeners are widely used for removing calcium and other deposit causing materials from so-called xe2x80x9chard water.xe2x80x9d The typical water softener relies on an ion exchange process taking place in an ion-exchange resin bed stored in a resin tank of the water softener. As the water to be processed passes through the resin filled tank, ions of calcium and other minerals in the water are exchanged with ions found in the resin, e.g., sodium, thereby removing objectionable ions from the water and exchanging them for less objectionable ions from the resin.
The capacity of the resin to exchange ions is finite and is reduced during the ion exchange process. If measures are not taken to regenerate the resin by replacing the undesirable ions with desirable ions, the ion exchange capacity of the resin, will become exhausted. Water softeners therefore are typically configured to periodically regenerate the ion exchange resin stored in the resin tank. Regeneration typically involves chemically replacing the objectionable ions such as calcium ions from the resin with less objectionable ions such as sodium ions. This replacement is typically performed by introducing a regenerant solution of sodium chloride or potassium chloride into the resin bed from a brine tank and thereafter flushing the regenerant solution from the bed. Regeneration of a water softener resin bed is sometimes accomplished in a direction that is co-current with the flow of water to be treated (often referred to as xe2x80x9cdownflow regenerationxe2x80x9d) and is sometimes accomplished in a direction that is countercurrent to the flow of water being treated (often referred to as xe2x80x9cupflow regenerationxe2x80x9d). The resin bed is typically backwashed in order to remove trapped particulate matter and rinsed to remove untreated backwash water from the lower portion of the resin bed. In order to prevent interruption of service, most water softeners are configured to allow bypass flow of untreated water directly to the treated water outlet during backwash, rinse, and regeneration. All of these operations are known in the art.
The regeneration cycle is typically controlled by a control valve mounted on top of the resin tank. The control valve is coupled to a source of untreated water, a treated water or service outlet line, the brine tank, a drain connection, and the resin tank. The typical control valve is controlled by an electric motor under the control of a timer and/or a usage indicator to cycle the water softener from service, brine introduction, backwash, fast rinse, and back to service.
Several different types of control valves have been used in water softeners. Some are of the rotary disc type, in which the motor rotates a three-dimensional disc to selectively connect and cover various inlet and outlet ports in the valve body bore in which the disc is mounted. A control valve of the type manufactured by Eco Water of Woodbury, Mn. Another control valve type, manufactured by Osmonics, comprises modified poppet valves. These multiple valve elements are independently actuated by cams. Still others are of the so-called reciprocating piston type, in which the motor drives a piston to reciprocate axially in a bore to selectively connect and cover various inlet and outlet ports in the bore. See, for example, U.S. Pat. Nos. 3,700,007 to Sparling and U.S. Pat. No. 4,290,451 to Fleckenstein et al. The invention relates to water softeners and other water conditioning units employing reciprocating piston-type control valves.
The typical reciprocating piston-type water softener control valve includes a seal arrangement that is positioned in a cylindrical bore and that surrounds the reciprocating piston. A piston is driven to reciprocate within the seal stack by a drive arrangement. The typical drive arrangement includes an AC electric motor and a motion converter that converts the rotary motion of the electric motor""s pinion to linear motion of the piston. Prior known motion converters comprised an offset cam or an offset linkage arrangement. Piston drive arrangements employing these motion converters exhibit several drawbacks.
For instance, they are nonreversible. As a result, they cannot be controlled to repeat any steps in the valve""s operational cycle. They also have a fixed path and, therefore, cannot be reprogrammed after initial assembly to skip one or more phases of the valve""s operational cycle. These drawbacks conspire to considerably restrict the range of applications of the typical water conditioning unit control valve and to prevent the operation of a water softener or other water conditioning unit that employs such a valve to be customized to meet a particular application""s needs. The pistons of these control valves are also subject to jamming because they cannot be backed away from an obstruction to permit the obstruction to clear the valve.
In addition, the support structure for the piston""s drive rod and the seals associated with that support structure are subjected to substantial side-loading by the associated motion converter. This side-loading can lead to accelerated wear and early failure of the motion converter and some of the system""s seals. It can also elevate the risk of valve element jamming.
The need therefore has arisen to provide a drive arrangement for a linearly reciprocating water conditioning unit flow control valve that includes a motion converter which converts the rotary motion of the arrangement""s motor to the linear motion of the piston of the control valve without imparting any side load on the support structure for the piston""s drive rod or its associated seals. The need also exists to provide a water conditioning unit flow control valve that is versatile so as to permit the operation of the water conditioning unit to be optimized for a particular application and to be varied as required to meet the current needs of the water conditioning unit.
In accordance with a first aspect of the invention, a water conditioning unit control device includes a reversible electric motor and a linearly reciprocatable piston that is driven without significant side loading on the support structure for the piston""s drive rod or the associated seals. Side loading is prevented by transferring torque from the motor to the piston arrangement using a converter which has an input coupled to the output element of the motor and which has an output which is coupled to the piston such that the piston moves linearly with the converter output. The converter converts bidirectional rotary motion of the motor output element to reciprocating linear movement of the piston. Preferably, the converter includes a lead screw arrangement comprising a driven gear and an externally threaded shaft or drive rod. The driven gear is driven by the output element of the motor and which has internal threads. The shaft extends through the driven gear in mating engagement with the threads thereof so as to move linearly relative to the driven gear upon rotation of the driven gear, and has a distal end portion which may be coupled to the piston or formed integrally with it.
The control valve may further comprise a stationary seal stack disposed in the bore and having a plurality of axially-spaced dynamic seals. In this case, the piston preferably has a plurality of axially-spaced lands thereon which selectively engage the dynamic seals to place selected ones of the ports into communication with one another.
In accordance with another aspect of the invention, a water conditioning unit control device is capable of varying the operation of the water conditioning unit without reconfiguring the structure of the control device and is capable of reacting to obstructions and other problems encountered by the control device. The control device includes a control valve, a reversible electric motor, and a controller. The control valve includes a piston which is movable linearly between a plurality of positions with respect to a valve bore of the control valve, thereby selectively connecting various ports in the valve bore to one another, the ports including at least an untreated water inlet port and a treated water outlet port. The motor, which may comprise a reversible DC motor, has an output element which is coupled to the piston and which is actuatable to drive the piston between the positions. The controller includes 1) an optical encoder or other position monitor which directly or indirectly monitors movement of the piston, and 2) a driver which is coupled to the position monitor and to the motor and which controls operation of the motor based on signals from the position monitor.
The motor preferably is a variable torque motor the output torque of which can be varied by varying the magnitude of drive current supplied thereto, and the controller preferably is operable, based on signals received from the position monitor, to determine whether the piston is stuck and to boost drive current to the motor if it is determined that the piston is stuck.
The controller preferably is operable, based on signals received from the position monitor, to determine whether the piston has encountered an obstruction. If it is determined that the piston has encountered an obstruction when traveling towards its intended position, the controller is operable to attempt to clear the obstruction by energizing the motor to back the piston away from the obstruction and by thereafter energizing the motor to drive the piston back towards the intended position.
In accordance with still another aspect of the invention, a method is provided that achieves at least some of the benefits of the water conditioning unit control devices described above.
These and other objects, advantages, and features of the invention will become apparent to those skilled in the art from the detailed description and the accompanying drawings. It should be understood, however, that the detailed description and accompanying drawings, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation.